• Energy Research

AbstractThe European Green Deal aims to reduce the use of chemical pesticides by half by 2030. Decision support systems are tools to help farmers schedule fungicide spraying based on disease risk and can reduce fungicide application frequency and overall use. However, the potential benefit of decision support systems compared to traditional calendar-based strategies has not yet been rigorously quantified. Here we synthesise 80 experiments and show that globally decision support systems can reduce fungicide treatments by at least 50% without compromising disease control. For a given fixed number of fungicide sprays, decision support systems were as effective as calendar-based programs in reducing disease incidence. When the number of sprays was halved, the increase in disease incidence was lower for decision support system-based strategies than calendar-based strategies. Our findings suggest that decision support systems can reduce fungicide use while limiting the risk to plant health and resistance development.

AbstractReliable estimates of the impacts of climate change on crop production are critical for assessing the sustainability of food systems. Global, regional, and site-specific crop simulation studies have been conducted for nearly four decades, representing valuable sources of information for climate change impact assessments. However, the wealth of data produced by these studies has not been made publicly available. Here, we develop a global dataset by consolidating previously published meta-analyses and data collected through a new literature search covering recent crop simulations. The new global dataset builds on 8314 simulations from 203 studies published between 1984 and 2020. It contains projected yields of four major crops (maize, rice, soybean, and wheat) in 91 countries under major emission scenarios for the 21st century, with and without adaptation measures, along with geographical coordinates, current temperatures, local and global warming levels. This dataset provides a basis for a comprehensive understanding of the impacts of climate change on crop production and will facilitate the rapidly developing data-driven machine learning applications.

Abstract Climate change is known to impact crop yields, mainly through increased temperatures, changing rainfall patterns and increasing CO2 concentration in the atmosphere. Although the potential effects of each of these factors have been discussed in a number of separate studies, no recent synthesis has been published to provide quantitative estimates of climate change impacts on crop yields, with or without adaptation strategies. In this paper, we synthetize a broad range of experimental or modeling studies to estimate, at the global scale, crop yield changes resulting from the marginal and combined effects of temperature, CO2 concentration and precipitation, with and without adaptation strategies. Crop yield sensitivities are estimated by distinguishing between C3 and C4 crops. For C3 crops, our results show that the positive effects of adaptation (+7.25 %) and CO2 (+9% for +100 ppm) are high enough to offset the negative effects of temperature increase (-2.4 % for +1 °C), even at +4 °C. On the other hand, for maize (i.e., the only C4 plant species in our database) the somewhat low positive effect from increased CO2 concentration and the absence of a significant effect of adaptation lead to higher yield losses, in the order of -10 % for +4 °C. The minimum level of CO2 concentration increase requested to achieve a yield gain under increased temperature conditions is much higher for maize than for C3 crops, in particular for wheat. The estimated effects of adaptation are uncertain, especially for soybean and rice, but also for maize, where the absence of a significant adaptation effect is probably at least partly due to limited data availability. Our results demonstrate that CO2 effects on crop yields should not be overlooked in foresight studies on the impacts of climate change. Our analysis also highlights the importance of improving our knowledge of how effective adapation strategies are in mitigating the impact of climate change.

Les événements extrêmes, tels que ceux causés par le changement climatique, les chocs économiques ou géopolitiques et les épidémies de ravageurs ou de maladies, menacent la sécurité alimentaire mondiale. La complexité de la causalité, ainsi que la myriade de façons dont un événement, ou une séquence d'événements, crée des impacts en cascade et systémiques, posent des défis importants à la recherche sur les systèmes alimentaires et aux politiques. Pour identifier les risques prioritaires pour la sécurité alimentaire et les opportunités de recherche, nous avons demandé à des experts de divers domaines et régions géographiques de décrire les principales menaces pour la sécurité alimentaire mondiale au cours des deux prochaines décennies et de suggérer des questions et des lacunes de recherche clés sur ce sujet. Nous présentons ici une hiérarchisation des menaces à la sécurité alimentaire mondiale résultant d'événements extrêmes, ainsi que des questions de recherche émergentes qui mettent en évidence les défis conceptuels et pratiques qui existent dans la conception, l'adoption et la gouvernance de systèmes alimentaires résilients. Nous espérons que ces résultats aideront à orienter le financement de la recherche et les ressources vers les transformations du système alimentaire nécessaires pour aider la société à faire face aux principaux risques du système alimentaire et à l'insécurité alimentaire en cas d'événements extrêmes. Los eventos extremos, como los causados por el cambio climático, las crisis económicas o geopolíticas y las epidemias de plagas o enfermedades, amenazan la seguridad alimentaria mundial. La complejidad de la causalidad, así como las innumerables formas en que un evento, o una secuencia de eventos, crea impactos en cascada y sistémicos, plantea desafíos significativos para la investigación y las políticas de los sistemas alimentarios por igual. Para identificar los riesgos prioritarios para la seguridad alimentaria y las oportunidades de investigación, pedimos a expertos de una variedad de campos y geografías que describieran las amenazas clave para la seguridad alimentaria mundial en las próximas dos décadas y que sugirieran preguntas y brechas clave de investigación sobre este tema. Aquí, presentamos una priorización de las amenazas a la seguridad alimentaria mundial derivadas de eventos extremos, así como preguntas de investigación emergentes que resaltan los desafíos conceptuales y prácticos que existen para diseñar, adoptar y gobernar sistemas alimentarios resilientes. Esperamos que estos hallazgos ayuden a dirigir la financiación de la investigación y los recursos hacia las transformaciones del sistema alimentario necesarias para ayudar a la sociedad a abordar los principales riesgos del sistema alimentario y la inseguridad alimentaria en situaciones extremas. Extreme events, such as those caused by climate change, economic or geopolitical shocks, and pest or disease epidemics, threaten global food security. The complexity of causation, as well as the myriad ways that an event, or a sequence of events, creates cascading and systemic impacts, poses significant challenges to food systems research and policy alike. To identify priority food security risks and research opportunities, we asked experts from a range of fields and geographies to describe key threats to global food security over the next two decades and to suggest key research questions and gaps on this topic. Here, we present a prioritization of threats to global food security from extreme events, as well as emerging research questions that highlight the conceptual and practical challenges that exist in designing, adopting, and governing resilient food systems. We hope that these findings help in directing research funding and resources toward food system transformations needed to help society tackle major food system risks and food insecurity under extreme events. وتهدد الأحداث المتطرفة، مثل تلك الناجمة عن تغير المناخ والصدمات الاقتصادية أو الجيوسياسية وأوبئة الآفات أو الأمراض، الأمن الغذائي العالمي. إن تعقيد السببية، فضلاً عن الطرق التي لا تعد ولا تحصى التي يخلق بها الحدث، أو سلسلة من الأحداث، تأثيرات متتالية ومنهجية، تشكل تحديات كبيرة لبحوث وسياسات النظم الغذائية على حد سواء. لتحديد مخاطر الأمن الغذائي ذات الأولوية وفرص البحث، طلبنا من خبراء من مجموعة من المجالات والمناطق الجغرافية وصف التهديدات الرئيسية للأمن الغذائي العالمي على مدى العقدين المقبلين واقتراح أسئلة وثغرات بحثية رئيسية حول هذا الموضوع. هنا، نقدم أولوية للتهديدات التي يتعرض لها الأمن الغذائي العالمي من الأحداث المتطرفة، بالإضافة إلى أسئلة البحث الناشئة التي تسلط الضوء على التحديات المفاهيمية والعملية الموجودة في تصميم وتبني وإدارة النظم الغذائية المرنة. نأمل أن تساعد هذه النتائج في توجيه تمويل البحوث والموارد نحو تحولات النظام الغذائي اللازمة لمساعدة المجتمع على معالجة المخاطر الرئيسية للنظام الغذائي وانعدام الأمن الغذائي في ظل الأحداث المتطرفة.

AbstractIn 2016, France, one of the leading wheat-producing and wheat-exporting regions in the world suffered its most extreme yield loss in over half a century. Yet, yield forecasting systems failed to anticipate this event. We show that this unprecedented event is a new type of compound extreme with a conjunction of abnormally warm temperatures in late autumn and abnormally wet conditions in the following spring. A binomial logistic regression accounting for fall and spring conditions is able to capture key yield loss events since 1959. Based on climate projections, we show that the conditions that led to the 2016 wheat yield loss are projected to become more frequent in the future. The increased likelihood of such compound extreme events poses a challenge: farming systems and yield forecasting systems, which often support them, must adapt.

The 2015/16 El Niño brought severe drought and record-breaking temperatures in the tropics. Here, using satellite-based L-band microwave vegetation optical depth, we mapped changes of above-ground biomass (AGB) during the drought and in subsequent years up to 2019. Over more than 60% of drought-affected intact forests, AGB reduced during the drought, except in the wettest part of the central Amazon, where it declined 1 y later. By the end of 2019, only 40% of AGB reduced intact forests had fully recovered to the predrought level. Using random-forest models, we found that the magnitude of AGB losses during the drought was mainly associated with regionally distinct patterns of soil water deficits and soil clay content. For the AGB recovery, we found strong influences of AGB losses during the drought and of γ . γ is a parameter related to canopy structure and is defined as the ratio of two relative height (RH) metrics of Geoscience Laser Altimeter System (GLAS) waveform data—RH25 (25% energy return height) and RH100 (100% energy return height; i.e., top canopy height). A high γ may reflect forests with a tall understory, thick and closed canopy, and/or without degradation. Such forests with a high γ ( γ ≥ 0.3) appear to have a stronger capacity to recover than low- γ ones. Our results highlight the importance of forest structure when predicting the consequences of future drought stress in the tropics.